1. Field of the Invention
The present invention relates to a wire or an induction wire installation device, and more specifically to a wire or induction wire installation device which permits easy and highly efficient installation of an optical fiber, cable, etc. even through a thin conducting wire tube having numerous bends and extending longer than 100 m or a thin tube coiled on a drum with an overall length of 1000 m or longer.
2. Prior Art
It has conventionally been a common practice to install a conducting wire or an induction wire through a pipeline or other small-diameter tube in office buildings, factories and communication facilities, and various installation means therefor has been developed. For instance, the installation means known include (a) the ones using compressed gas, such as air, inert gas, inactive gas, etc., and (b) ones using no compressed gas. In the former means using compressed gas, the method of supplying compressed gas through a tube passage and forcing a conducting wire or an induction wire thereinto is known. As an example of the latter means, the method of forcing a conducting wire or an induction wire into a tube passage with polyethylene pipe by hand is known.
However, in the former method, there is a great restriction on the diameter of a tube, and the smaller the tube diameter, the more difficult it is to install a wire therethrough. As the diameter becomes larger, safety problems occur due to the increased pressure of compressed gas. In addition, in the case of installation over a long distance or for a tube with numerous bends and coiled on a drum, it becomes exceedingly difficult to install a wire due to its contact with the inner wall of the tube.
On the other hand, by the method using no compressed gas, a conducting wire is manually forced into a tube, and accordingly such installation of a wire is in many cases difficult. Even when one can manage to install a wire over a short distance, it requires tremendous labor.
During recent years, there have been increasing numbers of cases where an optical fiber is employed as conducting wire. By the conventional installation method, it has been hard to install the fiber smoothly without any damage thereto, and by the method using compressed gas, it has been impossible to install an optical fiber with connection terminals attached thereto. For this reason, operators have been forced to make connections between the ends of optical fibers using a microscope after the completion of the difficult installation operation. Such labor requirements are a great burden on even experienced operators.
The inventor of the present invention has already proposed a new installation means which overcomes the above problems with the conventional installation method, and which permits easy installation of a wire even through a tube having numerous bends and extending as long as 100 m or longer, or a thin tube with an overall length of 1000 m coiled on a drum.
This apparatus operates on the basis of a Coanda spiral air flow to which the inventor of the present invention has been giving aggressive consideration for possible application to various fields of activities.
The Coanda spiral flow has features that differences in velocity and density between the axial flow along which the fluid flows and its surroundings are great, and that it has a steeper velocity distribution, i.e. the degree of turbulence is 0.09, less than half of 0.2 for turbulent flow, forming a different condition from turbulent flow. It also has a feature that a synthesis of an axial vector and a radial vector results in peculiar spiral air flow.
Using the fact that this spiral air flow is a flow which coverages along the tube axis in an in-tube flow, the method has been developed for installing a conducting wire at high efficiency without damage to the wire by use of this spiral air flow that has a small degree of turbulence and can control severe contact with the inner wall of a tube due to the automatic vibration of the wire.
FIG. 1 is a schematic drawing of the already proposed method and device for spiral air flow installation of a wire.
For instance, as shown in FIG. 1, a Coanda spiral air flow unit 3 is connected through a flexible hose 2 with a specified tube 1 in which a conducting wire is to be installed. To a central flow passage of this Coanda spiral air flow unit 3, compressed gas is supplied in the wire installing direction of the tube 1 through Coanda slits 4 thereof from a compressed gas supply means 5. Under this condition, a specified conducting wire 7 is inserted into the suction and induction port 6 of the Coanda spiral air flow unit 3.
The conducting wire 7 is automatically carried by a spiral air flow in the flexible hose 2 and the tube 1, causing wire installation to proceed at high speed.
As compressed gas supply means 5, a container of air, N.sub.2 or other compressed gas, or an air compressor can be utilized. When a container is used, it is acceptable if the container can keep the supply pressure of compressed gas to the Coanda spiral air flow unit 3 at approximately 5 to 20 Kg/cm.sup.2.
A typical example of the Coanda spiral flow unit 3 is shown in FIG. 2 in which an annular Coanda slit 4, the angled surface 9 in the close vicinity thereof, and a distribution chamber 10 for compressed gas are provided between the connection port to a tube 8 and the suction and induction port 6 through which a conducting wire is introduced.
By making the angle of the angled surface 9 about 5.degree.-70.degree., a spiral flow occurs and an intense vacuum suction force is generated at the suction and induction port 6, thereby guiding the conducting wire 7 to be installed through the tube 1 at high speed by a Coanda spiral flow.
The foregoing installation method and the device therefor provide excellent effectiveness and permit high-speed wire installation.
However, subsequent studies by the inventors have revealed that improvements can be made in the installation method and device using a Coanda spiral flow. More specifically, in the foregoing installation system, the occurrence of the back flow of compressed gas at the suction and induction port 6 cannot be avoided entirely, and there occurs a vibration and waving of a conducting wire 7. To ensure more stable installation at high speeds and over long distances, these problems must be solved.